London has been battered by 50mph winds that have felled trees and caused travel chaos. Powerful gusts swept across the capital as the Met Office issued a yellow "be aware" weather alert for most of the country.

President Barack Obama proposed a new assault weapons ban and mandatory background checks for all gun buyers on Wednesday in a bid to channel national outrage over the Newtown school massacre into the biggest U.S. gun-control push in generations.

Rolling out a wide-ranging plan for executive and legislative action to curb gun violence, Obama set up a fierce clash with the powerful U.S. gun lobby and its supporters in Congress, who are expected to resist what they see as an encroachment on constitutionally protected gun rights.

Obama presented his agenda at a White House event in front of an audience that included children from around the country, a poignant reminder of the 20 first-graders who were killed along with six adults by a lone gunman on Dec. 14 at Sandy Hook Elementary School in Newtown, Connecticut.

"While reducing gun violence is a complicated challenge, protecting our children from harm shouldn't be a divisive one," Obama said.

Until now, Obama had done little to rein in America's weapons culture during his first four years in office. But just days before his second inauguration, he appears determined to champion gun control in his next term with a concerted drive for tighter laws and other steps aimed at preventing further tragedies like the one at Newtown.

The proposals stem from a month-long review led by Vice President Joe Biden, who on orders from Obama met with advocates on both sides, including representatives from the weapons and entertainment industries.

Obama's plan calls on Congress for a renewed prohibition on assault weapons sales that expired in 2004, a requirement for criminal background checks on all gun purchases, including closing a loophole for gun show sales, and a new federal gun trafficking law - long sought by big-city mayors to keep out-of-state guns off their streets.

He also announced 23 steps he intends to take immediately without congressional approval. These include improvements in the existing system for background checks, lifting the ban on federal research into gun violence, putting more counselors and "resource officers" in schools and improved access to mental health services.

The most politically contentious piece of the package is Obama's call for a renewed ban on military-style assault weapons, a move that Republicans who control the House of Representatives are expected to oppose.

The Newtown gunman, 20-year-old Adam Lanza, used a Bushmaster AR-15 assault rifle to shoot his victims, many of them 6- and 7-year-olds, before killing himself.

Underscoring the tough political fight ahead, the National Rifle Association, launching a scathing advertising campaign against Obama's gun control effort and deployed its representatives in force on Capitol Hill.

The NRA, which says it has about 4 million members, took aim at Obama in a stinging TV and Internet spot, accusing him of being "just another elitist hypocrite" for accepting Secret Service protection for his two daughters but turning down the lobby group's proposal to put armed guards in all schools.

Obama's plan appears to tread cautiously on the question of whether violent movies and video games contribute to the gun violence, which would open up issues of freedom of expression.

A senior administration official said, however, that Obama would be asking for $10 million for the federal Centers for Disease Control and Prevention to study the root causes of gun violence, including any relationship to video games and media images.